The present invention relates to a high purity Ni—V alloy, high purity Ni—V alloy target and high purity Ni—V alloy thin film wherein the impurity content of Cr, Al and Mg and content of isotopic elements such as U and Th are reduced rigorously, and a purity of the Ni—V alloy is 99.5 wt % or higher, as well as to a manufacturing method thereof.
Today, although nickel-vanadium alloy is used as a part of a circuit element in a semiconductor device, in recent years, the circuit size is becoming small pursuant to the miniaturization of the semiconductor circuit. This miniaturization of circuit size requires the design and manufacture of highly sophisticated elements, and further requires the high purification and homogeneity of materials configuring these elements. The nickel-vanadium alloy, as described above, is used as a part of a circuit, but the impurities contained in the nickel-vanadium alloy are in particular becoming a problem.
A particular problem upon forming a microcircuit are the impurities of Cr, Al, Mg and radioactive isotopic elements such as U, Th contained in the nickel-vanadium alloy. Impurities of Cr, Al, Mg affect the etching characteristics (deteriorate the etching speed), and radioactive isotopic elements cause alpha decay and discharge alpha particles.
If the circuit element size is large as in the past, there would be no particular problem. Nevertheless, as described above, even slight amounts of alpha particles in a microcircuit would have an adverse effect on the electronic charge.
Further, upon forming a detailed circuit, improvement of the etching characteristics is a significant problem, and it is necessary that the target material and thin film material have few impurities and have superior uniformity.
As conventional technology, a proposal is made so as to make the alpha emission 10−2 counts/cm2 per hour or less in a nickel/vanadium sputtering target (c.f. Japanese Patent Laid-Open Publication No. 2000-313954).
Nevertheless, in this case, merely disclosed is a method of mixing raw material nickel having a purity of 99.98% and in which the alpha emission is 10−2 counts/cm2 per hour or less and raw material vanadium having a purity of 99.5% and in which the alpha emission is 10−2 counts/cm2 per hour or less, melting this with a vacuum fusion device, and rolling/annealing this to obtain a sputtering target.
In other words, the level of specific content of the individual radioactive isotopic elements to become a problem is still unclear, and there is no specific method (refining method) regarding how to reduce the individual radioactive isotopic elements which may have an adverse effect.
Therefore, conventionally, although it was known that alpha emission would have an effect in a microcircuit, there is a problem in that there is no specific method for reducing the individual radioactive isotopic elements and material for rigorously reducing the individual radioactive isotopic elements.
Further, there is no reference to the effect of impurities of Cr, Al, Mg on the etching characteristics, and such impurities are not even acknowledged as a problem. Nevertheless, uniformity of the material that affects the etching property is being sought upon forming a microcircuit.